1. Field of the Invention
The present invention related to a machine for use in the manufacture of slide fasteners, and more particularly to an apparatus for forming a space section devoid of coupling elements in a continuous slide fastener chain.
2. Prior Art
In order to properly finish ends of slide fasteners, it is necessary to form space sections or element-free gaps in a continuous slide fastener chain without injuring a pair of coupling elements located, respectively, next to endmost coupling elements lying at opposite ends of the respective gap to be formed. In a separable slide fastener adapted to open and close from opposite directions by manipulating a pair of sliders, it is further important to leave lateral projections on the pair of coupling elements uncut.
Various apparatus for providing such element-free sections or gaps in a continuous slide fastener chain are known, and they typically comprise a coacting punch and die unit and an indexing means for locating the slide fastener chain in the desired position relative to a cutting punch in the punch and die unit. Since the cutting punch has a rectangular horizontal cross section having cutting edges on its periphery, a pair of coupling elements located, respectively, next to endmost coupling elements lying at opposite ends of a gap to be formed is cut on respective lateral projections. Furthermore, due to cumulative errors in the coupling element pitch or the fastener tapes being locally elongated or shrunk, the fastener chain cannot always be brought to stop at the desired position in which a length of its elements, corresponding to the gap, register precisely with the cutting punch, in spite of the provision of the indexing means. If the fastener chain were processed for gap formation under such element conditions, the result would be that the terminal elements at either or both ends of the gap and either or both of the elements adjacent to such terminal elements are cut only partly away, with uncut debris interfering with a subsequent finishing operation.